Optical navigation sensors are conventionally used for surface navigation applications. For example, conventional optical navigation sensors are implemented in optical mouse devices for desktop computers. In surface optical navigation, the optical navigation sensor tracks the features of the navigation surface on which the device is moved.
More recently, optical navigation sensors have been used for free space navigation applications such as scene navigation. In some conventional embodiments, an optical navigation sensor for surface navigation is converted for use in free space applications by putting a wide angle lens on the optical sensor to track free space features. These conventional free space navigation devices are used for applications such as free-space presentation pointers and controllers. Other conventional technologies are also implemented to facilitate free space navigation operations. For example, some conventional free-space pointers use one or more mechanical gyroscopes (or gyro sensors) to provide navigation in the absence of surface features.
Despite the availability of individual surface and free space navigation devices, conventional optical navigation devices do not provide the functionality of both surface and free space navigation capability in a single device. When a user gives a presentation, for example using a desktop computer, the user typically uses a mouse and a separate pointer to navigate the presentation. The mouse provides surface navigation functionality, while the separate pointer provides free space navigation functionality.
Additionally, conventional surface optical navigation devices that are converted for use in free space navigation applications do not perform particularly well. While some conventional optical navigation devices implement image cross correlation based on images obtained by the sensor using a free space lens, such conventional technology has certain limitations. Many of these limitations originate from the failure of the free space navigation technology to control the light source for the scene. For example, conventional scene navigation devices have difficulty navigating in a low-light environment. Additionally, a light source that flickers (e.g., a fluorescent lamp or a television or computer monitor) results in an illusion that the optical navigation device is moving because the light flashes cause jitter, or noise, in the navigation signals.
Another problem with conventional free space optical navigation devices is the inability to navigate in environments with relatively few features. For example, conventional free space optical navigation devices have difficulty navigating using images of blank walls because the resolution of the imaged scene is too low to detect features of the blank wall. In comparison, surface optical navigation devices have relatively high resolution because of the proximity of the optical device and sensor to the surface features. However, once a surface optical navigation device is lifted or otherwise removed from close proximity with the navigation surface, it does not work properly and also fails to facilitate free-space navigation using free space images.
Another problem with conventional free space optical navigation devices is related to detection of three-dimensional movement of the optical navigation device. Conventional optical navigation devices for detecting three-dimensional movement are costly because they use two optical sensors. Using two optical sensors also consumes more power. Using multiple optical sensors also increases the complexity of the optical sensor design. In particular, it is more complex to integrate two sensors with a single microprocessor.